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NumberFormatException while parsing date with SimpleDateFormat.parse()

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我寻月下人不归
我寻月下人不归 2020-12-08 07:11

Have a function that creates a time-only Date object. (why this is required is a long story which is irrelevant in this context but I need to compare to some stuff in XML wo

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  • 广开言路
    广开言路 (楼主)
    2020-12-08 07:54

    SimpleDateFormat is not thread safe. the following program will reproduce NumberFormatException while parsing string represented date to date object.

    public class MaintainEqualThreadsPatallel {
    static int parallelCount = 20;
    public static void main(String[] args) throws Exception {
        ExecutorService executorPool = Executors.newFixedThreadPool(parallelCount);

        int numberOfThreads = 150; // Total thread count = 150*2= 300.
        List> futureReturns = new LinkedList>();
        for (int i = 0; i < numberOfThreads; i++) {
            int uniqueRandomValues = uniqueRandomValues(1, 10);

            // Callable Thread - call()
            Future submit = executorPool.submit( new WorkerCallable(uniqueRandomValues) );
            futureReturns.add(submit);

            // Runnable Thread - run()
            executorPool.execute( new WorkerThread(uniqueRandomValues) );
        }

        // WorkerCallable: Blocking main thread until task completes.
        waitTillThreadsCompleteWork(futureReturns);
        // Terminate Pool threads in-order to terminate main thread
        executorPool.shutdown();
    }
    private static final SimpleDateFormat sdf = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss");
    public static Date numberFormatEx(Date date) throws ParseException { // synchronized
        String dateStr = sdf.format(date);
        Date dateParsed = sdf.parse(dateStr); // NumberFormatException: For input string: "186E.2186E2"
        System.out.println("Date :"+ dateParsed);
        return dateParsed;
    }

    protected void loopFunction(int repeatCount) {
        String threadName = Thread.currentThread().getName();
        System.out.println(threadName +":START");
        for (int i = 1; i <= repeatCount; i++) {
            try {
                System.out.println(threadName +":"+ i);
                sleepThread(100);

                numberFormatEx(new Date());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        System.out.println(threadName +":END");
    }

    public static void waitTillThreadsCompleteWork(List> futureReturns) throws Exception {
        for (Future future : futureReturns) {
            int threadReturnVal = (int) future.get();
            System.out.println("Future Response : "+threadReturnVal);
        }
    }

    public static int uniqueRandomValues(int min, int max) {
        int nextInt = ThreadLocalRandom.current().nextInt(min, max);
        System.out.println("Random Vlaue : "+nextInt);
        return nextInt;
    }
    public void sleepThread(long mills) {
        try {
            Thread.sleep(mills);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
class WorkerThread extends MaintainEqualThreadsPatallel implements Runnable {
    int randomValue = 0;
    public WorkerThread(int randomValue) {
        this.randomValue = randomValue;
    }

    @Override
    public void run() {
        // As separate stack run() function doesn't accepts parameters, pass to constructor.
        loopFunction(randomValue);
    }
}
class WorkerCallable extends MaintainEqualThreadsPatallel implements Callable {
    int randomValue = 0;
    public WorkerCallable(int randomValue) {
        this.randomValue = randomValue;
    }

    public Object call() {
        // As separate stack run() function doesn't accepts parameters, pass to constructor.
        loopFunction(randomValue);
        return randomValue;
    }
}



    NumberFormatException with different messages:
    


    java.lang.NumberFormatException: multiple points
java.lang.NumberFormatException: For input string: ""
java.lang.NumberFormatException: For input string: "186E.2"
java.lang.NumberFormatException: For input string: "186E.2186E2"
java.lang.NumberFormatException: For input string: "22200222E.222002224EE4"

java.lang.NumberFormatException: For input string: "22200222E.222002224EE44"
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
    at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.lang.Double.parseDouble(Double.java:538)
    at java.text.DigitList.getDouble(DigitList.java:169)
    at java.text.DecimalFormat.parse(DecimalFormat.java:2056)
    at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1869)
    at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
    at java.text.DateFormat.parse(DateFormat.java:364)

    


    In Multi-Threading/Web Application with Multi-Requests concept parse function leads to NumberFormatException which can be handled using synchronized block.
    


    


    To overcome NumberFormatException on parse() function use any of the following scenarios.
    


      

    1. Separate Object: Every request/thread works on its own object.
      2. 

    


    public static Date numberFormatEx(Date date) throws ParseException {
    SimpleDateFormat ObjInstance = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss");
    String dateStr = ObjInstance.format(date);
    Date dateParsed = ObjInstance.parse(dateStr);
    System.out.println("Date :"+ dateParsed);
    return dateParsed;
}

    


    Unnecessary creating reusable object for each thread.
    


      

    1. Static Object synchronized block: Every request/thread shares the common object to perform operation. As multiple threads share same object at same time then the object data gets clear/overrride ""/"186E.2186E2" at some point and leads to error. 
      2. 

    


    static SimpleDateFormat objStatic = new SimpleDateFormat("dd-MMM-yyyy HH:mm:ss");
public static synchronized Date numberFormatEx(Date date) throws ParseException {
    String dateStr = objStatic.format(date);
    Date dateParsed = objStatic.parse(dateStr); // NumberFormatException: For input string: "186E.2186E2"
    System.out.println("Date :"+ dateParsed);
    return dateParsed;
}

    


    
  
    NOTE: In case of Memory management it better to use synchronized block with static object which is reusable.
    

    
    
    
             
    
                                                        
    
            
            
    
              
                
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